System and method for saving power in a wireless network by reducing power to a wireless station for a time interval if a received packet fails an integrity check

ABSTRACT

A method, an apparatus and a carrier medium storing instructions to implement the method. The method is in a first wireless station of a wireless network, and includes wirelessly receiving a signal corresponding to a packet wirelessly transmitted by a second wireless station. The packet includes a subpacket and a check sequence. The method further includes verifying the integrity of the subpacket, the verifying at least using the check sequence. The method further includes, in the case that the subpacket fails the verifying, reducing the power consumption of at least one component in the first wireless station for a time interval.

RELATED PATENT APPLICATIONS

This invention claims priority of and is a continuation of U.S. patentapplication Ser. No. 10/819,580 filed Apr. 6, 2004 to inventors Miller,et al., titled “A SYSTEM AND METHOD FOR SAVING POWER IN A WIRELESSNETWORK BY REDUCING POWER TO A WIRELESS STATION FOR A TIME INTERVAL IF ARECEIVED PACKET FAILS AN INTEGRITY CHECK,” Docket/Reference No.CISCO-7973. The contents of U.S. patent application Ser. No. 10/819,580are incorporated herein by reference.

This invention is also related to commonly assigned U.S. patentapplication Ser. No. 10/819,771, now U.S. Pat. No. 7,055,086, filed Apr.6, 2004 to inventor Lam titled “METHOD AND APPARATUS FOR PROTECTINGPARTS OF A PACKET IN A WIRELESS NETWORK.” The contents of U.S. patentapplication Ser. No. 10/819,771 are incorporated herein by reference,and hereby referred to as Lam.

BACKGROUND

This invention relates to wireless networks, to wireless stations of awireless network, and in particular to power saving in a wirelessstation of a wireless network such as a wireless local area network(WLAN). It is for example applicable to a wireless station that conformsto any of the OFDM variants of the IEEE 802.11 standard such as IEEE802.11a and IEEE 802.11g, and to future derivatives thereof.

Use of wireless networks such as wireless local area networks (WLANs) isbecoming widespread. A WLAN may be ad hoc, in that any wireless stationmay communicate directly with any other wireless station, or have aninfrastructure in which a wireless station can only communicate withanother station via a central station called an access point (AP). Theaccess point is typically coupled to other networks that may be wired orwireless, e.g., to the Internet or to an intranet. Wireless stations ofa wireless network thus wirelessly transmit and receive signals thatinclude modulated data over one or more transmission channels, totransmit data from one wireless station to another.

Portable wireless stations are a popular class of wireless stations usedin wireless networks. Such wireless stations include cellular phones,laptop computers, wireless digital cameras, battery-backed accesspoints, etc. Portable wireless stations are typically battery-poweredand the battery life is limited, e.g., they can only function for alimited time until the battery needs to be re-charged.

Such portable wireless stations increasingly use one of the orthogonalfrequency division multiplexing (OFDM) variants of the IEEE 802.11standard, e.g., IEEE 802.11a, IEEE 802.11g, etc. OFDM modulation breaksup data to be transmitted into several subcarriers, allowing for greatersignal reliability and transmission speeds. Unfortunately, multi-carrierfrequency approaches can sometimes translate into higher powerconsumption in a transmitting and/or receiving wireless station. Inother words, portable OFDM wireless stations can have a shorterbattery-powered lifetime compared to portable non-OFDM wirelessstations, e.g., portable wireless stations conforming to the IEEE802.11b standard.

Therefore there is a need in the art to provide a power saving methodand apparatus for a wireless station of a wireless network that usesOFDM.

A common power reduction technique is to simply turn off or put to alower-power mode-in either case called “put to sleep” herein-thosecomponents that are not being used and to then turn on (“wake up”) thosecomponents only when they are needed. The current IEEE 802.11 standardand its derivatives provide for a power save mode that allows for one ormore components of a wireless station to be put to sleep, e.g., thephysical (PHY) unit of a wireless station, for some portion of itsoperating period. A wireless station in power save mode essentially putsone or more components to sleep and then periodically wakes up thosecomponents necessary to transmit and/or receive transmissions. Aneighboring wireless station, e.g., another wireless station in anad-hoc network or an access point (AP) or client station in aninfrastructure network, buffers, e.g., stores, any packets destined tothe wireless station in power save mode until it transmits a request forsuch buffered packets.

Unfortunately the current IEEE 802.11 power save mode has a significantdrawback, namely that it is “coarse-grained:” when a wireless station isin power save mode, it only wirelessly receives packets in periodicintervals as defined by the standard. Such a power saving mode canaffect the latency, e.g., the responsiveness, of received transmissions.

Therefore there is a need in the art to provide a more fine-grainedpower saving method and apparatus for a wireless station of a wirelessnetwork.

SUMMARY

Disclosed herein are a method and a carrier medium storing instructionsto implement the method. The method is in a first wireless station of awireless network. The method comprises wirelessly receiving a signalcorresponding to a packet wirelessly transmitted by a second wirelessstation. The packet includes a subpacket and a check sequence. Themethod further comprises verifying the integrity of the subpacket, theverifying at least using the check sequence. The method furthercomprises, in the case that the subpacket fails the verifying, reducingthe power consumption of at least one component in the first wirelessstation for a first time interval.

Also disclosed herein is an apparatus. The apparatus is in a firstwireless station of a wireless network. The apparatus comprises aprocessing unit including a wireless transceiver coupled to an antenna.The processing unit is arranged to wirelessly receive a signalcorresponding to a packet wirelessly transmitted by a second wirelessstation. The packet includes a subpacket and a check sequence. Theapparatus further comprises a subpacket verifier coupled to theprocessing unit. The subpacket verifier is arranged to verify theintegrity of the subpacket, the verifying at least using the checksequence. The apparatus further comprises a power saver coupled to thesubpacket verifier. The power saver is arranged, in the case that thesubpacket fails the verifying, to reduce the power consumption of atleast one component in the first wireless station for a first timeinterval.

Also disclosed herein are a method and a carrier medium storinginstructions to implement the method. The method is in a first wirelessstation of a wireless network. The method comprises generating a checksequence to protect the integrity of a subpacket of a packet, whereinthe packet is to be wirelessly transmitted. The method further includesembedding the check sequence in an embedding field within the packet.The method further includes wirelessly transmitting the packet. Themethod is implemented such that a second wireless station wirelesslyreceiving a signal corresponding to the packet can verify the integrityat least using the check sequence of the subpacket. The method isfurther implemented such that, in the case that the subpacket fails theverifying in the second wireless station, the second wireless stationcan reduce power consumption of at least one component in the secondwireless station for a time interval.

Also disclosed herein is an apparatus. The apparatus is in a firstwireless station of a wireless network. The apparatus comprises aprocessing unit including a wireless transceiver coupled to an antenna.The processing unit is arranged to wirelessly transmit a packet. Thepacket includes a subpacket. The apparatus further comprises a checksequence generator coupled to the processing unit. The check sequencegenerator is arranged to generate a check sequence to protect theintegrity of the subpacket. The check sequence generator is furtherarranged to embed the check sequence in an embedding field within thepacket. The generating is implemented such that a second wirelessstation wirelessly receiving a signal corresponding to the packet canverify the integrity at least using the check sequence of the subpacket.The generating is further implemented such that, in the case that thesubpacket fails the verifying in the second wireless station, the secondwireless station can reduce power consumption of at least one componentin the second wireless station for a time interval.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a simplified block diagram of an apparatus in which aspectsof the present invention may be embodied. While FIG. 1 is labeled asprior art, the shown apparatus embodying one or more aspects of thepresent invention is not prior art.

FIG. 2A shows a Physical Layer Control Protocol (PCLP) header thatconforms exactly to the OFDM variants of the IEEE 802.11 standard. Whileit is labeled as prior art, such a header embodying one or more aspectsof the present invention is not prior art.

FIG. 2B shows the individual bits of the 5-byte PCLP header thatconforms to the present-day OFDM variants of the IEEE 802.11 standard.While it is labeled as prior art, such a header embodying one or moreaspects of the present invention is not prior art.

FIG. 3 shows a medium access control (MAC) frame including the MACheader that conforms to the IEEE 802.11 standard or a variant thereof.

FIG. 4 shows a network flow diagram roughly comparing four differentinterframe spacings (IFSs) used in the IEEE 802.11 standard and itsvariants or derivative standards.

FIG. 5 shows a common method in a wireless station of a wireless datanetwork conforming to an OFDM variant of the IEEE 802.11 standard forhandling detected errors in a received packet.

FIG. 6 shows a method embodying aspects of the present invention in awireless station of a wireless data network conforming to an OFDMvariant of the IEEE 802.11 standard for handling detected errors in areceived packet.

FIG. 7 shows a simplified block diagram of an embodiment of the presentinvention including a check sequence detector, a subpacket verifier, adestination determiner, and a power saver.

FIG. 8 shows a simplified block diagram of an embodiment of the presentinvention including a check sequence generator and an indicator unit.

FIG. 9 shows a simplified block diagram of an embodiment of the presentinvention including a check sequence detector, wherein one or moreelements are in the form of computer readable code in a memory.

DETAILED DESCRIPTION

Technology Background

Typical Wireless Apparatus

Transmissions in a wireless data network are typically logicallyorganized into a number of layers such as those found in theInternational Standards Organization (ISO)/Open Systems Interconnect(OSI) network model. The two lowest layers, called the physical (PHY)layer and the data link layer respectively, are usually implemented insome variation of an apparatus shown in FIG. 1. The PHY layer typicallymanages the raw transmissions at the physical level, e.g., theelectromagnetic level, and converts such raw transmissions to and frombits of data arranged in packets. The data link layer typically providesmanagement and control information for the data stream such as some ofthe error management for the PHY layer, flow synchronization informationand flow control information. For wireless networks that usemulti-access transmission channels such as wireless local area networks(WLANS), the data link layer is often subdivided to include a mediumaccess control (MAC) sublayer. The MAC sublayer, while considered bysome to also encompass some aspects of the PHY layer, is considered hereto be at the next layer up from the PHY layer.

FIG. 1 shows a simplified block diagram of an apparatus in which aspectsof the present invention may be embodied. While FIG. 1 is labeled asprior art, the shown apparatus embodying one or more aspects of thepresent invention is not prior art. The apparatus is logicallysubdivided into two separate components that respectfully handle thephysical layer and MAC sublayer of wireless data transmissions. Ofcourse, these two layers/sublayers may physically be handled by onepiece of hardware. The apparatus is typical and, for example, may beimplemented in a PCMCIA wireless local area network (LAN) card, amini-PCI card, or in an access point of a wireless network.

The apparatus 100 includes a physical (PHY) layer interface processor101 that include an antenna subsystem 103 with at least one antenna forthe frequency of service, e.g., approximately 2.4 GHz and/orapproximately 5 GHz for the one of the present IEEE 802.11 standards.The antenna subsystem 103, in the case of half-duplex operation,typically includes a transmit/receive switch, and for the case ofswitched diversity, typically includes a diversity switch to select anantenna.

The antenna subsystem 103 is coupled to a radio transceiver 105. Theradio transceiver 105 provides an analog received signal to and acceptsan analog signal for transmission from a modem 111. The radio receiverof the transceiver can include a low-noise amplifier and/or receiveradio frequency (RF) electronics. The radio transmitter part of thetransceiver can include transmit RF electronics and/or a poweramplifier.

The modem 111 includes a receiver part 113, including, e.g., ananalog-to-digital converter to digitize samples of the received signaland a demodulator/decoder. The modem 111 further includes a transmitterpart 115, including, e.g., a digital-to-analog converter and acoder/modulator. The modem further includes a control part 117. Forexample, the control part 117 can implement start of packet (SOP)detection, automatic gain control, etc. The modem 111 can be coupled tothe radio transceiver 105 via an analog interface for the receivedsignal and the signal for transmission, and also via a digital interfacefor control signals and status flags.

The apparatus 100 further includes a medium access control (MAC)processor 119 for MAC processing. The MAC processor 119 acceptsdecoded/demodulated data from the modem 111 and provides data to beencoded/modulated to the modem 111. The MAC processor 119 is furtherconnected to the modem 111 via another digital interface that providesaccess to the MAC processor 113 of various status flags and dataregisters in the modem 111.

The MAC processor 119 may optionally be coupled to a host processor 121via a host bus subsystem 123. While FIG. 1 shows a separate hostprocessor, the host processor function may optionally be incorporatedwith the MAC processor 119. A memory 125, e.g., a random access memoryelement (RAM), may be optionally included for program and/or datastorage. The memory 125 is sometimes directly coupled to the host or tothe MAC processor or to both. There may be additional memory, e.g., forbuffering, and such additional memory can either be included in memorysubsystem 125, or included in one or more components such as the MACprocessor 119, or both. One or more interfaces may be included inapparatus 100, e.g., one or more interfaces that conform to well-knownindustry standards such as PCMCIA, PCI, USB, etc.

Clearly other architectures are possible for the PHY and MAC parts of awireless station, and the invention is not limited to any particulararchitecture.

In some implementations, the transceiver, modem, and at least some ofthe MAC processor may be on the same processing unit, e.g., on the samechip.

IEEE 802.11 OFDM PLCP Header and MAC Frame

One embodiment of the invention is applicable to packets transmitted andreceived that conform to one of the OFDM variants of the IEEE 802.11standard, e.g., IEEE 802.11a, 802.11g, or derivatives thereof

Such an OFDM packet starts with a preamble that provides for start ofpacket detection, automatic gain control, diversity selection whendiversity is used, various other synchronization functions, and channelestimation. The preamble is followed by a modulated part.

FIG. 2A shows a Physical Layer Control Protocol (PCLP) header thatconforms exactly to present-day OFDM variants of the IEEE 802.11standard. While it is labeled as prior art, such a header embodying oneor more aspects of the present invention is not prior art.

The PLCP header is the first part of the modulated payload. In FIG. 2A,the PCLP header 200 includes a 3-byte SIGNAL field 201 that is modulatedat a low data rate. In particular, the SIGNAL field 201 is modulated atBinary Phase Shift Keying (BPSK) rate ½ and provides information aboutthe packet, including the data rate at which the rest of the packet isencoded. The SIGNAL field 201 is followed by a 2-byte SERVICE field 203that is modulated at the payload data rate specified in the SIGNAL field201. The remainder of the modulated payload, called the PLCP ServiceData Unit (PSDU), includes data at the payload data rate specified inthe SIGNAL field 201.

FIG. 2B shows the individual bits of the 5-byte PCLP header thatconforms to the present-day OFDM variants of the IEEE 802.11 standard.While it is labeled as prior art, such a header embodying one or moreaspects of the present invention is not prior art.

In FIG. 2B, the SIGNAL field 201 includes a RATE field of 4 bits denotedRate [0] through Rate [3] that provide information on the data rate. TheRATE information determines the coding rate and the modulation methodused for the modulated payload beyond the SIGNAL field 201. The RATEfield is followed by a reserved bit that is always 0, and a 12-bitLENGTH field whose bits are denoted Length [0] through Length [11]. TheLENGTH field is followed by an even parity bit. This is followed by6-tail bits of the SIGNAL field denoted Tail [0] through Tail [5] thatare unused bits that should be set to 0.

The three-byte SIGNAL field 201 is followed by the two-byte SERVICEfield 203 that includes 7 random scrambler initialization bits denotedScram_Init[0] through Scram_Init[6], and nine SERVICE field bits denotesService[7] through Service[15]. The latter are unused bits that shouldall be zero to conform exactly to the OFDM IEEE 802.11 standards. TheSERVICE field 203 is modulated at the same data rate as the rest of thepacket specified by the RATE field. U.S. patent application Ser. No.10/629,383 filed Jul. 28, 2003 to inventors Keaney, et al., titled“EARLY DETECTION OF FALSE START-OF-PACKET TRIGGERS IN A WIRELESS NETWORKNODE,” and assigned to the assignee of the present invention, describesthe inclusion in the SERVICE field information that helps protect theintegrity of such SIGNAL field that provides for a matching receiver toquickly determine whether or not a start of packet trigger is a falsestart of packet trigger. U.S. patent application Ser. No. 10/629,383 isincorporated herein by reference.

FIG. 3 shows a MAC frame including the MAC header that conforms to theIEEE 802.11 standard or a variant thereof. While it is labeled as priorart, such a header embodying one or more aspects of the presentinvention is not prior art.

In FIG. 3, the MAC frame 300 includes the MAC header 301 of 30 bytes,the data field 303 containing the data payload of 0 to 2312 bytes, and aframe check sequence (FCS) field 319 of 4 bytes. The MAC header 301includes a frame control field 303 of 2 bytes. The rest of the MACheader 301 includes a duration ID field 305 of 2 bytes, a source addressfield 307 of 6 bytes, a destination address field 309 of 6 bytes, areceiving station address field 311 of 6 bytes, a sequence control field313 of 2 bytes, and a transmitting station address field 315 of 6 bytes.Various fields may not be included depending on the type of 802.11 MACframe.

Wireless stations operating in independent basic service set (IBSS) modeor as access points must, according to the IEEE 802.11 standard, examinethe MAC header in all received packets, including management frames, tothe end of address 3 (311), regardless of destination address, for thepurposes of power save management. All wireless stations must examinethe MAC header in received packet, e.g., received control frames, to theend of address 1 (307) to determine which wireless station the MAC frameis for and to process the information in the duration ID field 305.

InterFrame Spacing

Aspects of the present invention incorporate interframe spacing topotentially increase aggregate transmission throughput between wirelessstations of a wireless network.

Wireless data networks such as WLANs typically operate over sharedchannels with the potential for transmission collisions. Protocols andstandards have been developed to manage transmissions on such wirelessdata networks. Typically transmission are broken into packets byreceivers and then reassembled by receivers. Packetization allows morethan one transmitter to send messages over the same channel during thesame aggregate time period.

One embodiment of the invention is applicable to packets of a wirelessnetwork that conforms to one of the IEEE 802.11 standards. Two generalmethods (protocols) are part of the IEEE 802.11 standard for managingshared channels over a wireless network. The distributed coordinationfunction (DCF) protocol is typically used to manage wirelesstransmissions in a wireless network configured for ad-hoc or in acentralized wireless network, e.g., a wireless network with an accesspoint (AP). The point coordination function (PCF) protocol may be usedto manage wireless transmissions in a centralized wireless network.

Interframe spacing (IFS) refers to standard time intervals that separatedifferent packets transmitted over a shared channel. Such time intervalsare used to manage data, e.g., packets, that use the shared channel.Different IFS intervals exist to better manage packet transmission andreception, packet discovery, collision-avoidance, etc.

FIG. 4 shows a flow diagram 400 that contrasts four different IFSintervals used as part of the IEEE 802.11 standard and its variants. Theshort IFS (SIFS) is a short idle time used for highest prioritytransmission such as ready to send (RTS), clear to send (CTS) andacknowledgment (ACK) packets. The PCF IFS (PIFS) is the minimum idletime for a typical packet transmission operating in PCF mode and islonger than SIFS. The DCF IFS (DIFS) is the minimum idle time fortypical packet transmissions and is longer than PIFS. The extended IFSis the minimum idle time when an error has occurred and is longer thanDIFS.

Error Correcting/Detecting Codes

Aspects of the present invention incorporate error correcting/detectingcodes to reduce power consumption in a wireless receiver.

There have been a number of techniques developed to detect and correcterrors in transmissions. Error-correcting codes (ECCs) anderror-detecting codes (EDC) are two classes of methods developed toovercome the problem of transmission errors. For wireless data networks,a wireless transmitter calculates and wirelessly transmits additionalredundant signal along with the original signal it wishes to protect.The wireless receiver can detect and/or correct errors in thetransmitted signal by performing a calculation using the received signaland the received redundant signal.

For wireless networks such as wireless data networks, redundant signalsin the form of check sequences, e.g., one or more bits of redundantdata, are often used to protect the integrity of part (or parts) of apacket, e.g., a subpacket. Check sequences are sometimes appended to theend of a subpacket. As an example, most additive checksum and polynomial(CRC) coding methods implemented today use appended check sequences. Inother cases, check sequences are sometimes inter-mixed with the data itprotects, e.g., Hamming codes.

An embodiment of a method in the patent application to Lam enables awireless transmitter to generate a check sequence for a subpacket to beprotected, e.g., where the check sequence is located in an embeddingfield located prior to the end of the subpacket. Such an embedding fieldcan comprise of a contiguous series of bits, or an arbitrary,non-necessarily contiguous subset of bits of the packet. Further, thischeck sequence is generated in such a way that a wireless receiverwirelessly receiving the packet can verify the subpacket withoutmanipulating or processing the check sequence, e.g., can verify thesubpacket assuming the check sequence is located at the end of thesubpacket. Such a method can reduce the complexity and cost in areceiving wireless station and is of importance to aspects of thepresent invention.

In one embodiment in the patent application to Lam, the check sequenceis a polynomial (CRC) code checksum. For many wireless data networkapplications, polynomial (CRC) codes are often used to protect parts ofa packet, e.g., subpackets of a packet. Polynomial codes sometimespreferable compared to other ECC and EDC method for their simplicity,low transmission costs, e.g., small check sequences, and higherror-detecting capability.

In one embodiment of the patent application to Lam, a wireless stationgenerates a check sequence by first computing an appended check sequenceand then multiplies the appended check sequence by a re-positioningmatrix. In another embodiment, an apparatus contains a multiplier unitto compute an appended check sequence and then multiplies the appendedcheck sequence by a re-positioning matrix. In another embodiment, themultiplier unit is implemented by a collection of XOR gates to form anXOR tree such that a multiplication can be calculated in O(log n) time.

In one embodiment of the related, above-mentionedincorporated-herein-by-reference U.S. patent application to Lam, one ormore bits of a reserved field are used to store such a check sequence.For OFDM variants of the IEEE 802.11 packet, such a reserved field canbe the SERVICE field of the packet. In another embodiment, a combinationof using the PARITY bit in the SIGNAL field and at least one bit of theSERVICE field are used to form a check sequence. In another embodiment,the PARITY bit in the SIGNAL field is instead used as an indicator fieldto indicate the presence of a check sequence in the SERVICE field.

Lower Power Modes

Aspects of the present invention utilize low-power modes, e.g., sleepmodes, to reduce power consumption in a wireless receiver.

Components of a wireless station are often split into two or moresub-components. Each component or sub-component can operate in a normaloperating mode, or alternately one or more low-power modes. A componentor unit operating in such a low-power mode is said to be sleeping orasleep. Implementations and techniques for implementing such low-powermodes are widely known in the art.

A Power Saving Method Using Check Sequences

Method in a Receiving Wireless Station

Aspects of the invention are incorporated in a method, an apparatus, anda carrier medium including one or more computer readable code segmentsto instruct one or more processors of a processing system to implement amethod.

In one embodiment of the invention, one or more check sequences of apacket are used to help determine whether or not to turn off one or morecomponents of a wireless station when receiving a transmission. Inparticular, if a part of a packet is found to be with error onreception, e.g., an integrity verification using a check sequence fails,it can be efficient to simply turn off those components related to thereceiving and processing functions until the end of the packet isreached. Additional aspects of the invention include methods to increasethe transmission throughput in addition to saving power.

FIG. 5 shows a common method in a wireless station of a wireless datanetwork conforming to an OFDM variant of the IEEE 802.11 standard forhandling detected errors in a received packet.

In FIG. 5, a method begins in the PHY processor following the processingof the preamble of the packet. Typically the first 3 bytes of the SIGNALfield are read (processed) to determine the RATE, LENGTH and PARITY 501.The PARITY bit is used to verify the integrity of the RATE and LENGTHfields. If the PARITY bit verification fails 503, then the PHY processortypically processes the rest of the packet as noise 505. The PHYprocessor must stay awake during the process to monitor the one or moretransmissions channel(s) for an end-of-packet characteristic, e.g., theclear-channel-assessment (CCA) going low. Following that, the MACprocessor typically performs a backoff using the DIFS timer 507, e.g.,treating the packet as if it was not directed to the wireless station.

If the PARITY bit verification succeeds 503, the MAC processor isnotified to begin processing the incoming bit stream 509. Typicallyintegrity verification for the rest of the bit stream is performed inthe MAC using the MAC FCS 511. If the integrity verification fails, theMAC processor performs a backoff using the EIFS timer 513, e.g.,treating the packet as if it contained a transmission error.

If the MAC frame verification succeeds 511, the MAC processor performs abackoff using the DIFS timer 517, e.g., treating the packet as if it wasreceived properly and the rest of the payload is processed by otherunits/components of the wireless station 515.

FIG. 6 shows a method embodying aspects of the present invention in awireless station of a wireless data network conforming to an OFDMvariant of the IEEE 802.11 standard for handling detected errors in areceived packet.

In FIG. 6, a method begins in the PHY processor following the processingof the preamble of the packet as in FIG. 5. Typically the first 3 bytesof the SIGNAL field are read (processed) to determine the RATE, LENGTHand PARITY 603. In one embodiment, the PARITY bit is used to verify theintegrity of the RATE and LENGTH fields. In another embodiment, theparity bit assumes odd parity instead of even parity in a variation withthe IEEE 802.11 standard. In another embodiment, a non-parity ECC/EDCmethod is used to verify the integrity of the SIGNAL field using a checksequence of at least one bit within the packet. In another embodiment,no PARITY bit verification is performed.

In one embodiment, if the PARITY bit verification fails 603, then thePHY processor processes the rest of the packet as noise 605. The PHYprocessor must typically stay awake during the process to monitor theone or more transmissions channel(s) for an end-of-packetcharacteristic, e.g., for the clear-channel-assessment (CCA) going low.In another embodiment, after the end-of-packet characteristic has beendetermined, the MAC processor performs a backoff using the DIFS timer607, e.g., treating the packet as if it was not directed to the wirelessstation.

In one embodiment, if the PARITY bit verification succeeds 603, the MACprocessor is notified to begin processing the incoming bit stream 609.In another embodiment, the integrity of at least one bit of the PLCPheader, e.g., the SIGNAL field, is verified using a polynomial (CRC)check sequence located in at least one bit of the SERVICE field. Inanother embodiment, the integrity verification includes, in addition toat least one bit of the PLCP header, at least one bit of the MAC header.In another embodiment, the verifying includes a polynomial (CRC) codechecksum calculation. In another embodiment, the verifying includes apolynomial (CRC) code checksum calculation using the generatorpolynomial of x⁸+x²+x+1. In another embodiment, integrity verificationis performed in the PHY processor before the MAC processor beginsprocessing the MAC frame (contrary to FIG. 6). In another embodiment,the MAC processor performs integrity verification. In anotherembodiment, the check sequence used for integrity verification isembedded, e.g., located prior to the end of the subpacket beingprotected. In another embodiment, the check sequence used for integrityverification uses at least one bit of the SERVICE field. In anotherembodiment, the integrity verification includes a calculationsubstantially conforming to a polynomial code checksum calculation.

In one embodiment of the invention, a check sequence is first detectedby checking for one or more non-zero bits of the SERVICE field. Inanother embodiment, a check sequence is first detected by checking forcertain values in one or more pre-defined fields of the packet. Inanother embodiment, the integrity verification is dependent uponascertaining whether there is a check sequence in the packet. In anotherembodiment, such an ascertaining uses at least one bit of the packet,e.g., detecting value of 1 where normally it is 0.

In one embodiment, if a check sequence doesn't exist, then the methodbypasses the PLCP/MAC header integrity verification 611. In anotherembodiment, the method does not check the PLCP/MAC header but proceedsto check the destination MAC address as in 617. In another embodiment,the destination MAC address is not checked at all and proceeds toverifying the entire MAC frame 623. In another embodiment, auser-settable parameter determines whether or not to check thedestination MAC address as in 617.

In one embodiment, if the PLCP/MAC header verification fails 611, thePHY processor is put to sleep for a time interval calculated using theRATE and LENGTH fields of the received PLCP header 613. In anotherembodiment, one or more components of a wireless station are put tosleep for another time interval calculated using the RATE and LENGTHfields. In another embodiment, one or more components of a wirelessstation are put to sleep for an arbitrary time interval. In anotherembodiment, the MAC processor performs a backoff using the DIFS timer615 in variance with the IEEE 802.11 standard, e.g., treating the packetas if it was not directed to the wireless station. In anotherembodiment, the MAC processor performs a backoff using the EIFS timer615, e.g., treating the packet as if it contained a transmission error.In another embodiment, the MAC processor can select either a DIFS orEIFS backoff using a user-configurable parameter. Using DIFS backoffs asdescribed in one or more embodiments of the present invention can resultin a transmission throughput performance gain in the wireless station,albeit the wireless station may no longer be in strict conformance withthe IEEE 802.11 standard.

In one embodiment, if the PLCP/MAC header integrity verificationsucceeds 611, the MAC processor begins processing the MAC header and theMAC payload. In one embodiment of the invention, the MAC destinationaddress is determined by examining contents of the MAC header. Inanother embodiment, the MAC destination address is determined using oneof the address fields of the MAC header depending on the To DS and FromDS fields of the Frame Control Field according to the IEEE 802.11standard, e.g., checking whether the destination address corresponds tothe receiving wireless station's wireless address. In one embodiment, ifthe destination check fails, the PHY processor is put to sleep for atime interval calculated using the RATE and LENGTH field of the receivedPLCP header 619. In another embodiment, one or more components of thewireless station are put to sleep for a time interval calculated usingthe RATE and LENGTH fields. In another embodiment, one or morecomponents of the wireless station are put to sleep for an arbitrarytime interval. In another embodiment, the MAC processor then performs abackoff using the DIFS timer 621. (According to the IEEE 802.11standard, the MAC processor must assume that the MAC header is valid dueto the earlier verification.)

In one embodiment, if the destination check succeeds 617, the MACprocessor is notified to begin processing the incoming bit stream asnormal. Typically verification is performed using the MAC FCS and theentire MAC frame 623. In one embodiment, if the verification fails 623,the MAC processor performs a backoff using the EIFS timer 625, e.g.,treating the packet as if it contained a transmission error.

In one embodiment, if the MAC frame verification succeeds 623, the MACprocessor performs a backoff using the DIFS timer 629, e.g., treatingthe packet as if it was received properly and the rest of the payload isprocessed by other units/components of the wireless station 627

Apparatus in a Receiving Wireless Station

The various embodiments of the method described above are substantiallyincorporated into one or components of an apparatus of a wirelessstation.

FIG. 7 shows a simplified block diagram of an embodiment of the presentinvention including a check sequence detector, a subpacket verifier, adestination determiner, and a power saver. The embodiment is similar tothe apparatus shown in FIG. 1 with additional aspects of the presentinvention. In FIG. 7, the apparatus 700 includes a physical (PHY) layerinterface processor (processing unit) 701 coupled to a MAC processor705.

In one embodiment, a check sequence detector 723 is located in thephysical (PHY) processor 701, and is incorporated into the modem 703 asshown in FIG. 7. In another embodiment, the check sequence detector 723is located in the MAC processor 705. In another embodiment, the checksequence detector 723 is connected to the MAC processor and/or thephysical (PHY) processor 701 via a data bus and/or data path. The checksequence detector 723 is arranged to ascertain whether there is a checksequence in a wirelessly received packet as described in the methodsubsection above. In one embodiment, the check sequence detector 723 iscoupled directly to the MAC processor 705. In another embodiment, thecheck sequence detector 723 is coupled to the MAC processor 705 throughthe modem 703.

In one embodiment, a subpacket verifier 725 is located in the physical(PHY) processor 701, and is incorporated into the modem 703 as shown inFIG. 7. In another embodiment, the subpacket verifier 725 is located inthe MAC processor 705. In another embodiment, the subpacket verifier 725is connected to the MAC processor and/or the physical (PHY) processor701 via a data bus and/or data path. The subpacket verifier 725 isarranged to verify the integrity of a subpacket as described in themethod subsection above. In one embodiment, the subpacket verifier 725is coupled directly to the MAC processor 705. In another embodiment, thesubpacket verifier 725 is coupled to the MAC processor 705 through themodem 703. In another embodiment, the subpacket verifier 725 is coupledto the check sequence detector 723.

In one embodiment, a destination determiner 727 is located in the MACprocessor 705 as shown in FIG. 7. In another embodiment, the destinationdeterminer 727 is located in the physical (PHY) processor 701. Inanother embodiment, the destination determiner 727 is connected to theMAC processor and/or the physical processor 701 via a data bus and/ordata path. The destination determiner 727 is arranged to determine adestination of the packet as described in the method subsection above.In one embodiment, the destination determiner 727 is coupled directly tothe physical (PHY) processor 701. In another embodiment, the destinationdeterminer 727 is coupled to the physical (PHY) processor 701 throughthe MAC processor 705. In another embodiment, the destination determiner727 is coupled to the check sequence detector 723. In anotherembodiment, the destination determiner 727 is coupled to the subpacketverifier 725.

In one embodiment, a power saver 729 is located in the MAC processor 705as shown in FIG. 7. In another embodiment, power saver 729 is located inthe physical (PHY) processor 701. In another embodiment, the power saver729 is connected to the MAC processor and/or the physical processor 701via a data bus and/or data path. The power saver 729 is arranged toreduce the power consumption of at least one component in the wirelessstation as described in the method subsection above. In one embodiment,one of the components for power reduction is the physical (PHY)processor 701. In another embodiment, the power saver 729 is coupleddirectly to the physical (PHY) processor 701. In another embodiment, thepower saver 729 is coupled to the physical (PHY) processor 701 throughthe MAC processor 705. In another embodiment, the power saver 729 iscoupled to the check sequence detector 723. In another embodiment, thepower saver 729 is coupled to the subpacket verifier 725. In anotherembodiment, the power saver 729 is coupled to the destination determiner727.

Method in a Transmitting Wireless Station

In one embodiment of the invention, a packet is generated andtransmitted by a first wireless station such that a second wirelessstation wirelessly receiving a signal corresponding to the packet canreduce power consumption and/or increase transmission throughput asdescribed in the method and apparatus of the previous subsections.

In one embodiment, a check sequence is generated to protect theintegrity of a subpacket of the packet to be wirelessly transmitted. Inanother embodiment, the check sequence is a check sequence, e.g., thecheck sequence is located in an embedding field prior to the end of thesubpacket. In another embodiment, the check sequence is a check sequencesuch that a wireless receiver receiving the packet can sequentiallyprocess the subpacket to verify the integrity of the subpacket as if thecheck sequence was appended at the end of the subpacket. An example ofsuch a method is described in the patent application to Lam.

In one embodiment, at least one bit of the packet to be transmitted isset to some value to indicate to a wireless station receiving the packetthat the packet contains a check sequence protecting a subpacket, e.g.,enabling a receiving wireless station to ascertain that a check sequenceprotecting a subpacket within a packet. In another embodiment, theembedding field for storing the check sequence is not located at the endof the packet. In another embodiment, generating the check sequenceincludes a calculation substantially conforming to a polynomial (CRC)code checksum calculation. In another embodiment, the packet to bewirelessly transmitted substantially conforms to one of the OFDMvariants of the IEEE 802.11 standard or a derivative thereof.

In one embodiment, the embedding field includes at least one bit of theSERVICE field. In another embodiment, the subpacket includes at leastone bit of a PLCP header and at least one bit of the MAC header. Inanother embodiment, the generating of the check sequence includes apolynomial (CRC) code checksum calculation. In another embodiment, thegenerating includes a polynomial (CRC) code checksum calculation usingthe generator polynomial of x⁸+x²+x+1. In another embodiment, such anintegrity verification is performed in the MAC processor. In anotherembodiment, such an integrity verification is performed in the PHYprocessor before the MAC processor begins processing the MAC frame(contrary to FIG. 6).

Apparatus in a Transmitting Wireless Station

The various embodiments of the method described above are substantiallyincorporated into one or more components of an apparatus of a wirelessstation.

FIG. 8 shows a simplified block diagram of an embodiment of the presentinvention including a check sequence generator and an indicator unit.The embodiment is similar to the apparatus shown in FIG. 1 withadditional aspects of the present invention. In FIG. 8, the apparatus800 includes a physical (PHY) layer interface processor (processingunit) 801 coupled to a MAC processor 805.

In one embodiment, a check sequence generator 823 is located in thephysical (PHY) processor 801, and is incorporated into the modem 803 asshown in FIG. 8. In another embodiment, the check sequence detector 823is located in the MAC processor 805. In another embodiment, the checksequence detector 823 is connected to the MAC processor and/or thephysical (PHY) processor 801 via a data bus and/or data path. The checksequence generator 823 is arranged to generate a check sequence toprotect the integrity of the subpacket and to embed the check sequencein an embedding field within the packet as described in the methodsubsection above. In one embodiment, the check sequence generator 823 iscoupled directly to the MAC processor 805. In another embodiment, thecheck sequence generator 823 is coupled to the MAC processor 805 throughthe modem 803.

In one embodiment, a indicator unit 825 is located in the physical (PHY)processor 801, and is incorporated into the modem 803 as shown in FIG.8. In another embodiment, the indicator unit 825 is located in the MACprocessor 805. In another embodiment, the indicator unit 825 isconnected to the MAC processor and/or the physical (PHY) processor 801via a data bus and/or data path. The indicator unit 825 is arranged toset at least one bit of a packet such that a wireless station canascertain whether there is a check sequence in the packet as describedin the method subsection above. In one embodiment, the indicator unit825 is coupled directly to the MAC processor 805. In another embodiment,the indicator unit 825 is coupled to the MAC processor 805 through themodem 803. In another embodiment, the indicator unit 825 is coupled tothe check sequence generator 823.

Wireless Station Coexistence

One aspect of the invention is setting one or more bits of an unusedportion of a packet substantially conforming to a wireless networkingstandard. In one embodiment, such a wireless networking standard is oneof the OFDM variants of the IEEE 802.11 standard or a derivativethereof.

One embodiment of the invention utilizes unused bits of the SERVICEfield of the packet to transmit additional data such as a checksequence. As such, wireless stations making use of one or moreembodiments of the present invention may co-exist on the same wirelessnetwork with other wireless stations that do not use any embodiments ofthe present invention.

Other Embodiments

FIG. 9 shows a simplified block diagram of an embodiment of the presentinvention including a check sequence detector, wherein one or moreelements are in the form of computer readable code in the memory of thehost processor. In particular, the apparatus 900 contains a hostprocessor 901 coupled to a memory 903. The memory 903 contains a carriermedium 905 that includes one or more computer readable code segments toinstruct the host processor 901 to implement a method. Such a method canbe any method embodiment of the present invention.

Another aspect of the invention involves the location of the embeddingfield. One embodiment of the invention requires the embedding field tobe located prior to the end of the subpacket to be protected. In anotherembodiment of the invention, the embedding field is not necessarily asubset of the subpacket to be protected, e.g., the embedding field is asubset of the packet but not necessarily entirely included in thesubpacket to be protected. In another embodiment of the invention, theembedding field is entirely located in the subset of the subpacket to beprotected.

One aspect of the invention makes use of one or more bits of a packet toindicate to a receiver receiving the packet that a frame in the packetcontains a check sequence. In one embodiment of the invention, atransmitter sets one or more bits of a packet to a value, e.g., settingone or more bits of the indication field to 1 when they are normally 0,etc. In another embodiment of the invention, a receiver determineswhether or not the packet includes a check sequence by checking theindication field, e.g., checking if one or more bits of the indicationfield are set to 1 when they are normally 0. In another embodiment ofthe invention, the check sequence includes the indication field. Inanother embodiment of the invention, an apparatus contains an indicationunit to indicate that the frame contains a check sequence. In anotherembodiment of the invention, an apparatus contains an indication unit todetermine whether or not a frame includes a check sequence.

In one embodiment of the invention, a calculation substantiallyconforming to a polynomial (CRC) code checksum calculation occurs whengenerating a check sequence. In another embodiment of the invention, acalculation substantially conforming to a polynomial (CRC) code checksumcalculation occurs when verifying a frame containing a check sequence.In yet another embodiment of the invention, such calculations occur inboth the generating of a check sequence and the verifying of a framecontaining a check sequence.

Variations

It is well known in the art that the arrangement of bits in a sequencedepends on the context of the application. For example, a particularbit-order depends on the protocols/standards that are employed andunderlying/dependent hardware and/or software that is used, e.g.,most-significant bit (MSB) order vs. least-significant bit (LSB) order.Furthermore, different encoding schemes may interleave or scramble bitsfrom one context to another. In other words, bits in a “logical” contextmay not necessarily be ordered in the same way that bits in a “real”context are ordered. It is also well known in the art that dataprocessor units may not necessarily process packets sequentially intheir respective bit-order. Thus, no attempt has been made to explicitlyenumerate all the possible bit-orderings for transmitting, receiving,processing and/or generating bits of data. Therefore, all possiblebit-ordering and bit-encoding schemes, and their derivatives andvariants, are hereby incorporated as alternate embodiments of theinvention.

Those in the art will be aware that the logical “end” of an arbitrarypart of a packet, e.g., a subpacket, is dependent on context. Inparticular, a check sequence being “appended” to the end of a subpacketof a packet, can have at least three different interpretations dependingon context. In one case, a subpacket contains a pre-defined field at theend of the subpacket that is used to store the check sequence. Anexample of this is the IEEE 802.11 MAC frame that contains a 4-byteframe check sequence (FCS) field. In another case, the end of thesubpacket does not contain a pre-defined field at the end, and as such,the processing unit processing the subpacket adds a check sequence tothe end of the subpacket, thereby extending the subpacket's length. Anexample of this includes many standard CRC modules (both in software andhardware). In yet another case, the embedding field for the subpacket islocated before the end of the subpacket. An example of this are themethods for embedding a check sequence described in the patentapplication to Lam. Therefore, all such variations to the “end” of aregion or “before the end” of a region are hereby incorporated asalternate embodiments of the invention.

Embodiments of the invention are able to protect arbitrary,not-necessarily contiguous regions of a packet. Furthermore, fieldswhere check sequences are located, e.g., embedding fields, are alsonot-necessarily contiguous regions. Thus, it is to be clearly expressedthat subpackets, embedding fields, check sequences, or any generic fieldof a packet may not necessarily be contiguous and may occupy differentlevels or sublevels of a packet. Therefore all possible contiguous andnon-contiguous variations to such regions are hereby incorporated asalternate embodiments of the invention.

The application refers to copying, embedding, inserting, replacing, etc.as descriptive but generically equivalent phrases to refer to the act ofsetting one or more states of a packet, buffer, field, memory region,etc. Therefore, it is to be clearly recognized that no further action iseither implied or intended by using descriptive phrases when referringto the act of setting one or more states of a packet, buffer, memoryregion, etc.

Those in the art will understand that there are many variations of theimplementation of the apparatus shown in FIG. 1, which are incorporatedinto many aspects of the present invention. There has not been anattempt to describe all possible variations and as such, it should beappreciated that many common variations, derivatives and modificationsexist. Therefore, all such variations, derivatives and modifications arehereby incorporated as alternate embodiments of the present invention.

It is well known in the art that there are many variations andderivatives of the general polynomial (CRC) coding method. Manypolynomial (CRC) coding standards have been established in the art.Examples of some CRC coding standards include CRC-8, CRC-12, CRC-16,CRC-CCITT, XMODEM-CRC and CRC-32. Embodiments of the invention may makereference to one or more polynomial (CRC) code methods. Althoughpolynomial (CRC) code standards exist, embodiments of the presentinvention are not limited to any particular polynomial (CRC) codestandard, nor are they limited to any particular variation of derivativeof the general polynomial coding method. Thus all such variations andderivatives are hereby incorporated as alternate embodiments of theinvention.

One embodiment of the invention uses the embedding of a check sequenceas described in the incorporated herein by reference patent applicationreferred as “Lam.” In Lam, in one embodiment, the check sequence isgenerated such that a wireless station wirelessly receiving a signalcorresponding to a transmitted packet containing a protected subpacketcan sequentially verify the integrity of the subpacket as if the checksequence were appended at the end of the subpacket being protected, suchas would occur with a typical polynomial, e.g., CRC verifier thatassumes there is a check sequence appended at the end. Thus, a prior artpolynomial, e.g., CRC verifier can verify such a check sequence. By thisis included the case that the wireless station can serially verify theintegrity of the subpacket without needing to process the check sequencemore than once, i.e. more than when first encountered. By this is alsoincluded the case that the wireless station can verify the integrity ofthe subpacket without needing to storing, e.g., to buffer the embeddedcheck sequence. All these cases are meant to be included in the phrase“sequentially verify the integrity of the subpacket as if the checksequence were appended at the end of the subpacket being protected.”

In several embodiment of the invention, the wireless network and/or thepackets being transmitted/received over the wireless networksubstantially conform to an OFDM variant of the IEEE 802.11 standard ora derivative thereof. It is well known in the art that the invention isnot limited to such contexts and may be utilized in various wirelessnetwork applications and systems. Furthermore, embodiments or aspects ofthe invention are not limited to any one type of architecture orprotocol, and thus, may be utilized in conjunction with one or acombination of other architectures/protocols. For example, the inventionmay be embodied in devices conforming to other standards and for otherapplications, including other WLAN standards, Bluetooth, IrDA, and otherwireless communication standards. Thus, all such contexts are herebyincorporated as alternate embodiments of the invention.

One embodiment of each of the methods described herein is in the form ofa computer program that executes on a processing system, e.g., one ormore processors that are part of wireless station of a wireless network.Thus, as will be appreciated by those skilled in the art, embodiments ofthe present invention may be embodied as a method, an apparatus such asa special purpose apparatus, an apparatus such as a data processingsystem, or a carrier medium, e.g., a computer program product. Thecarrier medium carries one or more computer readable code segments forcontrolling a processing system to implement a method. Accordingly,aspects of the present invention may take the form of a method, anentirely hardware embodiment, an entirely software embodiment or anembodiment combining software and hardware aspects. Furthermore, thepresent invention may take the form of carrier medium (e.g., a computerprogram product on a computer-readable storage medium) carryingcomputer-readable program code segments embodied in the medium. Anysuitable computer readable medium may be used including a magneticstorage device such as a diskette or a hard disk, or an optical storagedevice such as a CD-ROM.

It will be understood that the steps of methods discussed are performedin one embodiment by an appropriate processor (or processors) of aprocessing (e.g., computer) system executing instructions (codesegments) stored in storage. It will also be understood that theinvention is not limited to any particular implementation or programmingtechnique and that the invention may be implemented using anyappropriate techniques for implementing the functionality describedherein. The invention is not limited to any particular programminglanguage or operating system.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner, as would beapparent to one of ordinary skill in the art from this disclosure, inone or more embodiments.

Similarly, it should be appreciated that in the above description ofexemplary embodiments of the invention, various features of theinvention are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureand aiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the Detailed Description are hereby expressly incorporatedinto this Detailed Description, with each claim standing on its own as aseparate embodiment of this invention.

It should further be appreciated that although the invention has beendescribed in the context of wireless networks, the invention is notlimited to such contexts and may be utilized in various otherapplications and systems, for example in a node of a cellular phonenetwork or in a system that uses radio transmission to communicate viasatellite. Furthermore, the invention is not limited to any one type ofnetwork architecture and method of encapsulation, and thus may beutilized in conjunction with one or a combination of other networkarchitectures/protocols.

All publications, patents, and patent applications cited herein arehereby incorporated by reference.

Thus, while there has been described what is believed to be thepreferred embodiments of the invention, those skilled in the art willrecognize that other and further modifications may be made theretowithout departing from the spirit of the invention, and it is intendedto claim all such changes and modifications as fall within the scope ofthe invention. For example, any formulas given above are merelyrepresentative of procedures that may be used. Functionality may beadded or deleted from the block diagrams and operations may beinterchanged among functional blocks. Steps may be added or deleted tomethods described within the scope of the present invention.

1. A method in a first wireless station of a wireless network, themethod comprising: wirelessly receiving a signal corresponding to apacket wirelessly transmitted by a second wireless station, wherein thepacket includes a subpacket and a check sequence; verifying theintegrity of the subpacket, the verifying at least using the checksequence; and in the case that the subpacket fails the verifying,reducing the power consumption of at least one component in the firstwireless station for a first time interval.
 2. A method as recited inclaim 1, wherein the verifying includes a calculation substantiallyconforming to a polynomial code checksum calculation.
 3. A method in afirst wireless station of a wireless network, the method comprising:generating a check sequence to protect the integrity of a subpacket of apacket, wherein the packet is to be wirelessly transmitted; embeddingthe check sequence in an embedding field within the packet; andwirelessly transmitting the packet; such that a second wireless stationwirelessly receiving a signal corresponding to the packet can verify theintegrity of the subpacket at least using the check sequence and, in thecase that the subpacket fails the verifying, can reduce powerconsumption of at least one component in the second wireless station fora time interval.
 4. A method as recited in claim 3, wherein thegenerating includes a calculation substantially conforming to apolynomial code checksum calculation.
 5. An apparatus in a firstwireless station of a wireless network, the apparatus comprising: aprocessing unit including a wireless transceiver coupled to an antenna,the processing unit arranged to wirelessly receive a signalcorresponding to a packet wirelessly transmitted by a second wirelessstation, wherein the packet includes a subpacket and a check sequence; asubpacket verifier coupled to the processing unit arranged to verify theintegrity of the subpacket, the verifying at least using the checksequence; and a power saver coupled to the subpacket verifier arranged,in the case that the subpacket fails the verifying, to reduce the powerconsumption of at least one component in the first wireless station fora first time interval.
 6. An apparatus as recited in claim 5, whereinthe subpacket verifier is located inside the processing unit.
 7. Anapparatus as recited in claim 5, wherein the subpacket verifier isfurther arranged to include a calculation substantially conforming to apolynomial code checksum calculation.
 8. An apparatus in a firstwireless station of a wireless network, the apparatus comprising: aprocessing unit including a wireless transceiver coupled to an antenna,the processing unit arranged to wirelessly transmit a packet, whereinthe packet includes a subpacket; and a check sequence generator coupledto the processing unit, the check sequence generator arranged togenerate a check sequence to protect the integrity of the subpacket andto embed the check sequence in an embedding field within the packet,such that a second wireless station wirelessly receiving a signalcorresponding to the packet can verify the integrity of the subpacket atleast using the check sequence and, in the case that the subpacket failsthe verifying, can reduce power consumption of at least one component inthe second wireless station for a time interval.
 9. An apparatus asrecited in claim 8, wherein the check sequence generator is furtherarranged to include a calculation substantially conforming to apolynomial code checksum calculation.
 10. A carrier medium including oneor more computer readable code segments to instruct one or moreprocessors of a processing system to implement a method in a firstwireless station of a wireless network, the method comprising:wirelessly receiving a signal corresponding to a packet wirelesslytransmitted by a second wireless station, wherein the packet includes asubpacket and a check sequence; verifying the integrity of thesubpacket, the verifying at least using the check sequence; and in thecase that the subpacket fails the verifying, reducing the powerconsumption of at least one component in the first wireless station fora first time interval.
 11. An apparatus in a first wireless station of awireless network, the apparatus comprising: means for wirelesslyreceiving a signal corresponding to a packet wirelessly transmitted by asecond wireless station, wherein the packet includes a subpacket and acheck sequence; means for verifying the integrity of the subpacket, theverifying at least using the check sequence; and means for, in the casethat the subpacket fails the verifying, reducing the power consumptionof at least one component in the first wireless station for a first timeinterval.